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This article aims to provide an overview of successive seismic zonations in mainland France and probabilistic seismic hazard studies performed over the previous ${\approx }$30 years. A short presentation is given on the engineering and regulatory framework that shapes the background of seismic zonation and hazard studies, followed by a scientific overview of published probabilistic seismic hazard estimations. The components of these past PSHA studies are summarized (seismic source models, ground-motion models, management of uncertainties). The evolution of hazard estimates with time is displayed for a set of representative cities. Finally, three generations of official seismic zonation maps in France are presented (1967, 1986, 2004), and the evolution of methods and results is highlighted. This review shows that the academic community has previously had little involvement in this topic. As current zonation relies on outdated models, there is an opportunity for scientific and engineering communities to efficiently work together to build the next generation of probabilistic seismic hazard models for France.

The 2020 update of the European Seismic Hazard Model (ESHM20) is the most recent and up-to-date assessment of seismic hazard for the Euro-Mediterranean region. The new model, publicly released in May 2022, incorporates refined and cross-border harmonized earthquake catalogues, homogeneous tectonic zonation, updated active fault datasets and geological information, complex subduction sources, updated area source models, a smoothed seismicity model with an adaptive kernel optimized within each tectonic region, and a novel ground motion characteristic model. ESHM20 supersedes the 2013 European Seismic Hazard Model (ESHM13; Woessner et al., 2015) and provides full sets of hazard outputs such as hazard curves, maps, and uniform hazard spectra for the Euro-Mediterranean region. The model provides two informative hazard maps that will serve as a reference for the forthcoming revision of the European Seismic Design Code (CEN EC8) and provides input to the first earthquake risk model for Europe (Crowley et al., 2021). ESHM20 will continue to evolve and act as a key resource for supporting earthquake preparedness and resilience throughout the Euro-Mediterranean region under the umbrella of the European Facilities for Seismic Hazard and Risk consortium (EFEHR Consortium). [ABSTRACT FROM AUTHOR]

PREdiction of NOn-LINear soil behavior (PRENOLIN) is an international benchmark aiming to test multiple numerical simulation codes that are capable of predicting nonlinear seismic site response with various constitutive models. One of the objectives of this project is the assessment of the uncertainties associated with nonlinear simulation of 1D site effects. A first verification phase (i.e., comparison between numerical codes on simple idealistic cases) will be followed by a validation phase, comparing the predictions of such numerical estimations with actual strongmotion recordings obtained at well-known sites. The benchmark presently involves 21 teams and 23 different computational codes. We present here the main results of the verification phase dealing with simple cases. Three different idealized soil profiles were tested over a wide range of shear strains with different input motions and different boundary conditions at the sediment/bedrock interface. A first iteration focusing on the elastic and viscoelastic cases was proved to be useful to ensure a common understanding and to identify numerical issues before pursuing the nonlinear modeling. Besides minor mistakes in the implementation of input parameters and output units, the initial discrepancies between the numerical results can be attributed to (1) different understanding of the expression “input motion” in different communities, and (2) different implementations of material damping and possible numerical energy dissipation. The second round of computations thus allowed a convergence of all teams to the Haskell–Thomson analytical solution in elastic and viscoelastic cases. For nonlinear computations, we investigate the epistemic uncertainties related only to wave propagation modeling using different nonlinear constitutive models. Such epistemic uncertainties are shown to increase with the strain level and to reach values around 0.2 (log10 scale) for a peak ground acceleration of 5 m=s2 at the base of the soil column, which may be reduced by almost 50% when the various constitutive models used the same shear strength and damping implementation.

In the framework of site-specific seismic hazard assessment, the definition of reference motion is a crucial step. Reference motion is generally associated with hard-rock conditions, characterized by S-wave velocity exceeding 1500 m/s. However, ground motion recorded at sites with such conditions is poorly represented in existing strong-motion databases. Thus, the validity domains of most empirical ground-motion prediction equations (GMPEs) are not representative of reference rock conditions. To overcome this limitation and assess ground motion at reference conditions, the so-called "deconvolution approach" was proposed by Laurendeau et al. (2018) to correct surface recordings from theoretical 1DSH site response before GMPE developments. With the same purpose, in this article, we propose to apply the deconvolution approach using empirical site-response estimates as an alternative to theoretical ones. Using the Kiban-Kyoshin network (KiK-net) data, we estimate empirical site responses at KiK-net stations using generalized inversion techniques in addition to those from 1DSH numerical simulations, as presented in the companion article. Finally, a reference ground-motion model (RGMM) is determined based on empirically deconvolved ground motions. The advantage of using empirical rather than 1DSH site responses in the deconvolution approach is that in the former case the RGMM can be built based on records from an extensive set of sites, whereas the latter case is restricted to well-characterized sites with dominant 1D behavior. This makes the proposed approach easily exportable to different regions of the world, where precise site characterizations are not systematically available, and the knowledge of site behavior is limited. [ABSTRACT FROM AUTHOR]

Site-specific seismic hazard assessment involves the prior knowledge of (1) the input ground motion at the local bedrock and (2) the site response. In this article and its companion, we address the deconvolution approach to obtain a reference ground-motion model, which consists of removing site effects from surface ground-motion recordings. Laurendeau et al. (2018) applied this approach on the KiK-net network with site response from 1D SH-wave (1DSH) simulations, calculated using the VS profiles available for most sites. Indeed, this approach presents several limitations with 1DSH site response if it is considered to be applied to other networks, especially in the European context. First, the approach requires identification of sites with dominant 1D effects. Second, it needs the presence of accurately measured VS profiles. In this context, we propose to derive deconvolved ground-motion models using site response from generalized inversion techniques () for two main reasons. The first reason is that the GIT delivers empirical site response for all types of sites, conditioned by the presence of sufficient amount of data, and the second is that it reduces the need for VS profiles. We focus on the estimation of site effects from different approaches and present a methodology to obtain reliable site terms from GIT based on the experience from previous studies. We also introduce and detail the difference between absolute and relative site response, which mainly depends on the chosen reference. We estimate and compare site response for the KiK-net stations with different methods, that is, empirical and theoretical 1DSH. We also conclude a list of 1D sites based on comparisons between theoretical and empirical estimates of site response. The results obtained in this article will be the primary input for the deconvolution approach applied in the companion article. [ABSTRACT FROM AUTHOR]